OCR Text |
Show that HCN is normally the first measurable volatile nitrogen species. The appearance of fuel nitrogen as NH3 in the gas phase may be important during char oxidation or during high temperature gasification of low rank coals as indicated by experimental data of Brown, et al.27 Prompt NO formation and NO recycle reactions have been neglected in the NOx model used in this study. Thermal NO formation is governed by the extended Zel'dovich mechanism. 28-29 The theory and evaluation of the NO model is described in more detail by several workers.3-6 Experimental Measurements In this study, the NOx model was evaluated by comparing model predictions with effluent measurements made in a pulverized, coal-fired utility boiler.30 The boiler is the Goudey Station power plant unit #8, boiler #13 in Johnson City, New York, which is operated by New York State Electric and Gas Co. The furnace is a tangentially-fired, forced-recirculation, pulverized coal unit with an 85 MWe gross generating capacity. The furnace is comer-fired with four levels of burners in each corner. The coal burners are surrounded by secondary plenums which carried the remaining combustion air into the furnace. In all of the tests performed in this study, there was no coal in the secondary streams. The injection angle of the burners can be varied either up or down. A schematic drawing of the furnace is shown in Figure 2, which illustrates the different regions of the furnace as well as the dimensions. Comparisons with In situ measurements from this boiler for two different coal types have been reported previously for temperatures, major species (02 and C02) and NO concentrations. These comparisons showed good agreement between measured and predicted values.24 In the experimental program, ten tests were performed by the New York State Electric and Gas (NYSEG) Company to measure NOx pollutant emissions under various operating conditions. They were designed to evaluate variations in unit operation and simulate control techniques known to affect NOx formation. The operating conditions being considered were: over-fire air, burner 4 |